The present invention relates to a vortex flow meter.
U.S. Pat. No. 4,891,988 assigned to the assignee of this application discloses a vortex flow meter using a pressure sensor.
Japanese Utility Model Publication No. 54-3725 discloses a pressure difference detection of Karman vortex in which a pair of pressure conducting holes and a pair of detection chambers are provided and the detection chambers are separated from each other by a pair of pressure difference detecting elements.
Japanese Utility Model Publication No. 61-4808 discloses a use of a pair of diagphrams to prevent an erroneous operation of a flow meter due to vibration of the diagphrams.
Japanese Kokai (P) 60-100026 discloses a pressure sensor in which a pair of diaphragms are arranged differentially to remove residual distorsion applied to the diagphrams.
Japanese Kokai (U) 59-180625 or Japanese Kokai (U) 63-36851 discloses another typical example of a conventional vortex flow meter. The vortex flow meter shown in either of them comprises a vortex generating post, a pair of movable partitions capable of being deviated by vortex generated by the vortex generating post, two pairs of detectors for detecting deviations of these movable partitions as complementary electric variations and a bridge circuit including these detectors.
In the vortex flow meter constructed as mentioned above, a Karman vortex sensor portion is provided integrally with a conduit and, therefore, a pressure distorsion such as vibration or mechanical shock exerted on the conduit may be transmitted to a cavity in which a pressure sensor is formed, causing the cavity to be distorted slightly. Such small distorsion of the cavity is transmitted through a medium, i.e., air, to the movable partitions, i.e., diagphrams, resulting in an erroneous output from the bridge circuit.